Question
QUESTION: i have 8 falcon heads that are not rotating.(they can be manually rotated)..is there a repair process to get them to rotate again? (at $30 a head, i am hoping there is a fix.

ANSWER: Falcon heads require a substantial amount of pressure and flow to work correctly.  Make sure your control valve is open halfway or a little more.  Make sure any main shutoff is fully open.  You can also reduce the flow through the sprinkler, and maintain line pressure by installing a smaller nozzle on the heads.

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QUESTION: i am certain that pressure is not an issue. can you take the sprinkler apart? can you soak it in calcium remover? can you spray it with silicon and if so where and how would you spray?

Answer
You can unscrew the cap from the body of the sprinkler and clean out the internal filter, but lubrication is not recommended, because they are built to be water lubed.  I would look for other problems like a restriction in the line, a leak or a malfunctioning valve.